1. Field of the Invention
The invention is related to the field of optical amplification, and in particular, to optical amplifier systems and methods for amplifying Coarse Wavelength Division Multiplexing (CWDM) channels using optical amplifiers having fluoride-based optical fiber.
2. Statement of the Problem
Many communication companies use fiber optic cabling as a media for transmitting data because of its high bandwidth capacity. The optical fibers of a fiber optic cable can reliably transport optical signals over short or long distances. For shorter distance networks, such as a Fiber to the Premises (FTTP) network or a Metro Access network, Coarse Wavelength Division Multiplexing (CWDM) has been used as a cost effective way to transport voice and data over CWDM channels. CWDM networks reduce the overall cost of a network by using widened channel spacing. The International Telecommunication Union (ITU) defined CWDM channels as channels having 20 nm spacing. Because of the wide channels spacing, CWDM networks can use less expensive lasers to transmit optical signals making them desirable for certain applications.
One concern with CWDM networks is capacity. Because of the 20 nm spacing between CWDM channels, not as many channels can be used which results in a limited capacity. To add capacity to a CWDM network, network administrators can replace a CWDM channel with multiple Dense Wavelength Division Multiplexing (DWDM) channels. Typical DWDM channels have a channel spacing of less than 2 nm. Multiple DWDM channels can be used in the place of a CWDM channel, which increases the capacity of the network. The lasers of a DWDM network are more expensive than the lasers of a CWDM network, but they may be necessary to add the needed capacity. Networks deploying both CWDM channels and DWDM channels are referred to as CWDM/DWDM hybrid networks.
Another concern with CWDM networks or CWDM/DWDM hybrid networks is distance. There currently is not an effective solution for amplifying the multiple CWDM channels to prolong the distance of a CWDM network. Most current CWDM networks do not have any amplification between the core network and the customer premises. Some vendors have proposed using Semiconductor Optical Amplifiers (SOA) to amplify the CWDM channels if distance becomes an issue. Unfortunately, no practical solution for using SOAs has been proposed. Individual SOAs would have to be equipped for each CWDM channel because of the SOA's low optical output power and severe degradation due to fiber nonlinearity effects. Another amplification solution for CWDM networks or CWDM/DWDM hybrid networks is needed.